The present invention relates to downhole tools for use in cased or lined well bores for the oil and gas industry, and in particular to a downhole tool which includes a barrier between the tool body and well bore wall which is actuable to control fluid flow past the tool.
It is considered desirable when drilling for oil or gas to maintain a clean interior in the casing or liner of the drilling well. For this purpose, well cleaning equipment is well known and comes in a variety of different forms, including casing scrapers, brushes and circulation tools. Such equipment is used to free the well tubing from debris particles, cement lumps, rocks, congealed mud and so on.
Indeed well clean-up apparatus is used in an attempt to clean the casing or other well tubing of even smaller particles or debris such as oxidation lumps, scale and burrs for example.
More advanced clean-up tools have also been developed which filter the well fluid downhole. This is done to remove the debris prior to production of the well. Such filtering tools generally operate by providing a barrier in the annulus between the tool body and the wall of the well casing or liner. The barrier causes diversion of fluid flowing past the tool into the tool. Once inside the tool the fluid is passed through a filter and then directed back into the annulus on the opposite side of the barrier. Such a tool is that disclosed in GB 2335687.
A major disadvantage of these tools is that, as filtering is required in one flow direction through the tool, a second flow path through the tool must be provided for fluid flow in the opposite direction so that the tool can be run in and/or pulled out of the well bore without re-dispersing the collected debris. This additional flow path restricts the volume of fluid which can pass the tool and may be prone to clogging if unfiltered well fluid is required to take this flow path on running in.
It is an object of the present invention to provide a downhole tool which allows for selective bypass of fluid around the outer body of the tool.
It is a further object of at least one embodiment of the present invention to provide a downhole tool with an actuable barrier which can be used to selectively divert fluid through the tool body.
It is a yet further object of at least one embodiment of the present invention to provide a downhole tool with an actuable barrier which can be used to selectively divert fluid passing the tool body through the tool body when the tool is run-in, pulled out or is stationary within the well bore.